1. Field of the Invention
This invention relates to a chuck for tools such as drills.
2. Description of the Prior Art
Conventionally, a typical example of this type of chuck for tools has been known as disclosed in Japanese Patent Publication No. 55-25002 (U.K.P. No. 1468639) and will be explained herein with reference to FIG. 1 in the accompanying drawings.
This prior art chuck has a main body 1 and in the forward end portion of the main body 1, a center hole 4 is bored which extends axially in order that the shank of a tool T is received in the center hole 4. This center hole 4 branches at equal angular intervals to a plurality of (typically three) slanting holes 5 which extend obliquely toward the rear of the chuck, and jaws 2 are slidably inserted in the slanting holes 5.
Each jaw 2 has, at its forward end, an inner surface 6 which extends in parallel with the axis line of the main body 1, and when the jaws 2 are advanced forwardly (to the left in the illustration), they clamp the tool T as shown in FIG. 1. Threaded on the rearward outer surface of each jaw 2 is a male screw 7 which meshes with a female screw 8 of a rotary member 3 rotatably received in an annular groove 9 formed in the main body 1. The rotary member 3 is formed, at its forward end, with a bevel gear 10. The main body 1 has a radial blind hole 11.
With the chuck for tools constructed as above, in order to move the jaws 2 within the main body 1, a tip end shape 12 of a handle 13 is inserted to the blind hole 11 to bring a bevel gear 14 of the handle 13 into meshing engagement with the bevel gear 10 and the rotary member 3 is then rotated by rotating the handle 13. This rotation of the rotary member 3 cooperates with the screws 7 and 8 to move the jaws 2 along the slanting holes 5, so that the tool T may be clamped by the jaws 2 when they are advanced and released from the jaws 2 when they are retreated.
This prior art chuck for tools needs the separate handle 13, independent of the chuck per se, for the purpose of moving the jaws 2 and it is impossible to move the jaws 2 without using the handle 13. If the handle 13 is lost or can not be found at hand, one may try to clamp or release the tool T by rotating the rotary member 3, but the rotary member 3 may only be rotated together with the main body 3 and the trial may be done in vain, indicating a failure to acccomplish the intended purpose.